Optimum design of steel frames with rigid and different semi rigid connection types using stochastic search techniques

In this study, weight optimization of planary steel frames is made according to different column-beam joint types. Static analysis of steel structures is performed while assuming column-beam joints as hinge or completely rigid. In the fact, the behavior in these joints is not hinge and completely rigid. The behavior of joints is between these two behaviors and this behavior is named as partly restrained or behavior of semi rigid column-beam. In rigid joints, it is known that there isn?t any rotation between column and beam, on the other hand rotation may occur even in very low moment values in hinge joints. In semi rigid connections, moment transfer by the joint and some rotation under the effect of moment are possible to mention. This situation increases (P-?) effects in the structure with the displacement due to rotation of joint and contribution of vertical loads. This case effects the moment distribution in the structure. This situation shall be taken into consideration in structural analyses by the assumption of the semi rigid behavior of joints in the fact. Possible rotation behavior in joints is modelled by springs in the structure and flexure of joints shall also be taken into consideration. Semi rigid connections in the literature as end plate with stiffeners, end plate without stiffeners, top and seat angle with web angles and header plate models are taken in this study and weight change of structures according to joint types are investigated. First of all, the structures are modeled according to rigid connection assumption, then modeled according to semi rigid connection types and weights of the structures are compared. Sizing of the structures are made according to cases proposed AISC-LRFD code. All column and beams in the structure are selected from W section profiles. Particle swarm and hunting search techniques are used by taking strength, displacement and geometrical conditions in column-beam joints into consideration to select the profile sections which provide the minimum weight of the structure in proper solutions. Birds, fishes and insects move together to survice in the nature. For example, when birds fly together to forage, they find the food they wanted in a short time. Particle swarm optimization method is a searching technique which imitates the forage behavior of bird flock. Column and beam sections which provide the least structure weight is searched in optimization process as similar to foraging of birds. Each bird moving in a flock represents a proper solution for optimization process. Hunting search, which is another optimization technique used in the study, occurs from the strategies which are developed by animals as lion and wolf while searching their preys and imitating these behaviors. There is a definite duty for each prey in the scope of the strategy developed by preys as flocks. Moving flocks may catch the stronger, faster and bigger animals which in a short time with the developed strategy. In hunting search, each predator is a part of the problem solution. Effort of predators while hunting for their preys equals optimum search of the solution. Design of rigid and semi rigid steel frames are completed for the structures having minimum weight as objective function by using algorithms in particle swarm and hunting search techniques